1. Field of the Invention
The present invention relates to a CMOS driver for driving a large capacitive load, and more particularly to a bootstrapped CMOS driver for a low-voltage application.
2. Description of the Background Art
In general, a CMOS VLSI circuit having a large fan-out or a long interconnect metal line or a CMOS output pad driver have a considerably large capacitive load. Accordingly, design of a driver circuit for driving a large capacitive load is very important for the driver circuit itself determines an operation speed of the system.
FIG. 1 illustrates a conventional tapered CMOS driver 1 to drive a large capacitive output load. As shown therein, the tapered CMOS driver 1 consists of a chain of inverters each of which employs a large size transistor progressing toward to a load.
However, when being scaled a supply voltage to reduce power consumption, there is a problem in that the operation speed of the tapered CMOS driver 1 is considerably reduced, because a threshold voltage of a MOS device constituting each inverter can not be reduced at the same rate as the supply voltage. Accordingly, to overcome such a problem, there has been introduced a BiCMOS driver that uses a driving capacity of a bipolar device. But, to apply the bipolar device to the CMOS process technology, a high cost premium is required.